**6. Field effects (3): ecological effects**

First, *synergistic effects* with other environmental factors, including climate conditions and chemical stressors, may exist in the wild. When an organism experiences stress from a single source, the stress may be managed relatively well; however, when stress is imposed by two different sources, the harmful effects may be synergistically enhanced beyond their individual actions. In laboratory conditions, the "climate" conditions are usually constant, and additional stressors are not usually provided; thus, synergy is often difficult to predict using conventional irradiation experiments alone. Logically, the synergistic effects of radiation exposure and other stressors have been an important topic in radiation biology [52, 53, 58–61]. However, in my opinion, such synergistic stress effects have not been fully appreciated in radiation biology. Importantly, synergistic stress effects are not limited to exposure to radiation. Here, I briefly discuss two examples that may be insightful for this line of discussion.

**Figure 2.** Four possible types of effects on the larvae of the pale grass blue butterfly (green bars). Molecular ionization is the direct (i.e., primary) effect, while the other three modes (synergistic stress, particulate matter, and plant chemicals)

A discrepancy has been recognized between the laboratory and field results in phenotypic plasticity studies. In an authoritative textbook, Gilbert and Epel [62] stated the following: "Phenotypic plasticity means that animals in the wild may develop differently than those in the laboratory" and "This has important consequences when we apply knowledge gained in the laboratory to a field science such as conservation biology." One specific example provided in the textbook states that some frog tadpoles are up to 46 times more sensitive to pesticides in the presence of predators that release chemicals in the wild than they are in the laboratory [63, 64]. The conclusion stated that "ignoring the relevant ecology can cause incorrect estimates of a pesticide's lethality in nature" [63]. I believe that the same principle

Another insightful case was reported in the epidemic caused by the bacterium *Clostridium difficile* [65, 66]. For this bacterial epidemic outbreak to occur in North America and Europe, the widespread use of a food additive, trehalose, played a crucial role. Infected mice had higher mortality rates when fed food that contained trehalose [66]. Without the trehalose-rich environment that newly emerged in this century, the deadly endemic would not have occurred.

applies to radioactive materials from nuclear reactors.

are biological indirect (i.e., secondary) field effects.

56 New Trends in Nuclear Science

Third, when one examines the interactions of multiple species based on a food web or an ecological system as a whole, one may be able to discover radiation effects that would not be discovered by a single-species approach; consequently, observations like this may indicate important field effects. This may be called *the ecological effects*. A similar concept has recently been addressed in radioecology [76]; however, this topic is often discussed from the viewpoint of the bioaccumulation of radioactive materials or organic materials in high-order consumers. Although bioaccumulation is important, it is based on a dosimetric viewpoint.

The ecological system that the pale grass blue butterfly inhabits is relatively simple due to its monophagous nature [48]. Thus, this butterfly and its associated ecosystem may serve as a "model ecosystem" to investigate both the population dynamics and the environmental influences through the ecological food web after the Fukushima nuclear accident. It appears that in the case of the pale grass blue butterfly "model ecosystem," the quality of its host plant, *Oxalis corniculata*, is probably important and is determined by the quality of the soil and air. When soil is contaminated with radioactive materials and other pollutants, such as agrochemicals, the quality of the host-plant leaves decreases. Similarly, air pollutants (i.e., particulate matter) that cover the surface of leaves, whether radioactive or not, may change the physiological functions of the leaves. Thus, the quality of the soil and air will affect the health of the larval butterflies that eat the affected leaves.

The consequences of allergic reactions are complex, but one example of a type of reaction is kidney failure, which can include *nephrotic syndrome*; I have reported a case in which nephrotic syndrome was likely induced by the immunological field effects of the Fukushima nuclear accident [86]. Indeed, a general relationship between immunological sensitization and nephrotic syndrome has been demonstrated [87–92]. This relationship has not been rigorously tested; however, this is not surprising because nephrotic syndrome is a collection of

Understanding Low-Dose Exposure and Field Effects to Resolve the Field-Laboratory Paradox…

http://dx.doi.org/10.5772/intechopen.79870

59

Regarding the first mode of the field effect discussed above, the synergistic effects are potentially numerous in human society and in human living environments. One of the potential stressors is cedar pollen, which causes Japan-wide allergic reactions in the spring of each year, including 2011 immediately before and after the Fukushima nuclear accident. It is possible that the aerosol from the Fukushima reactors attached to cedar pollen to worsen *pollen allergy* (i.e., *hay fever*). Other potential stressors for humans may include other air pollutants, food additives, agrochemicals, and work stress. Stress resistance varies among individual humans, and some people that were not very stress resistant may have become sick after the

Regarding the third mode of the field effects discussed above, changes in plant chemicals may affect human health. Additionally, the nutritional quality of fruits and vegetables may have declined. However, different from the pale grass blue butterfly, humans are not monophagous. Moreover, vitamin supplementation is now popular in many countries including Japan. As such, this type of field effect may not manifest in humans; however, this mode may cause

Because the field effects of "nuclear" pollution may be a new concept, at least to some extent, misunderstanding or confusion about this issue may prevail. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2017 Report [93] provides an example. This report mentioned our studies in paragraph 125, in which H8 refers to Hiyama et al. [9], and M9 and M10 refer to Møller et al. [19] and Møller et al. [20],

*125. The Committee had made reference to studies in which effects in various terrestrial biota had been observed in areas with enhanced levels of radioactive material as a result of the FDNPS accident [H8, M9, M10]. It had noted that the substantial impacts reported for populations of wild organisms from these studies were inconsistent with the main findings of the Committee's theoretical assessment. The Committee had expressed reservations about these observations, noting that uncertainties with regard to dosimetry and possible confounding factors made it difficult to substantiate firm conclusions from* 

It is understandable that our study is "inconsistent with the main findings of the Committee's theoretical assessment" (i.e., the dosimetric simulations). I agree that "uncertainties with regard to dosimetry" should be overcome in the near future; however, without precise dosimetric data, the findings that conclude the biological effects were correlated with the

diseases that have various etiologies.

Fukushima nuclear accident.

**8. UNSCEAR 2017 Report**

*the cited field studies.*

respectively.

serious adverse impacts in the pale grass blue butterfly.

The decrease in plant quality for larvae may originate from two different causes: a decrease in certain favorable chemicals (e.g., essential nutrients) in leaves and an increase in unfavorable chemicals (e.g., reactive oxygen species and defense chemicals) in leaves. In the former scenario, the lack of an essential vitamin in the leaves may be fatal for butterfly larvae because larvae are dependent on vitamins that are supplied through the ingestion of leaves. A similar case of thiamine (vitamin B1 ) deficiency has been recognized as one of the major consequences of environmental pollution and destruction in Europe and North America; however, the precise causes of this deficiency are difficult to identify [77–80].

The latter possibility of the decrease in plant quality for butterfly larvae may occur if plants are stressed by even low levels of exposure to radioactive materials; this exposure can produce reactive oxygen species, defense chemicals, or another substance that is harmful to larvae. Reactive oxygen species are known to be produced by various abiotic stressors, and the production of defense chemicals are induced by insect bites in many plants [81–83]; however, whether radiation stress can trigger such responses in *O. corniculata* and in plants in general is unknown. The upregulation of unfavorable chemicals and the downregulation of favorable chemicals for larvae may occur simultaneously.

Consequently, biochemical changes in producers (i.e., plants) affect primary consumers (i.e., herbivorous animals) and then secondary consumers (i.e., carnivorous animals). These foodmediated effects of pollutants can radiate through an ecological food web, and it is indirect field effects that are different from the bioaccumulation paradigm. It is reasonable to imagine that damage to keystone species that have connections with many other species may cause relatively large effects on the ecosystem; however, recent research posits that anthropogenic disturbances on a small number of any species may cause instability in an ecosystem [84, 85].
